Semiconductor device and method of driving transistors

Abstract

When a driving unit ( 100 ) charges gate input capacitance ( 6 ) of an IGBT ( 7 ), the gate input capacitance ( 6 ) accumulates electric charges which are accumulated therein when the driving unit ( 100 ) discharges the gate input capacitance ( 6 ). Therefore, it is possible to reduce the amount of electric charges to be supplied to the gate input capacitance ( 6 ) by the driving unit ( 100 ) until the charge of the gate input capacitance ( 6 ) is completed. As a result, it is possible to reduce the required power capacity of a control power supply ( 15 a ). Further, since the electric charges accumulated in the gate input capacitance ( 6 ) are effectively used, it is possible to ensure power savings of a semiconductor device. Thus provided are a semiconductor device and a method of driving a transistor, in which electric charges accumulated in gate input capacitance of an insulated gate transistor are effectively utilized, to reduce required power capacity of a power supply for driving the transistor and ensure power savings of the semiconductor device on the whole.

What is claimed is:  
     
       1. A semiconductor device comprising: 
       an insulated gate transistor;  
       a driving unit for producing charge and discharge of gate input capacitance of said insulated gate transistor; and  
       at least one capacitor linked to said charge and said discharge produced by said driving unit to be selectively connected to a gate of said insulated gate transistor,  
       wherein said at least one capacitor is linked to said discharge produced by said driving unit to be connected to said gate, whereby said gate input capacitance supplies said at least one capacitor with electric charges accumulated therein and said at least one capacitor accumulates therein said electric charges supplied from said gate input capacitance, and said at least one capacitor is linked to said charge produced by said driving unit to be connected to said gate, whereby said at least one capacitor supplies said gate input capacitance with said electric charges accumulated therein and said gate input capacitance accumulates therein said electric charges supplied from said at least one capacitor.  
     
     
       2. The semiconductor device according to  claim 1 , wherein said at least one capacitor is connected to said gate in advance of said discharge produced by said driving unit and said gate input capacitance supplies said electric charges accumulated therein to said at least one capacitor. 
     
     
       3. The semiconductor device according to  claim 1 , wherein said at least one capacitor is connected to said gate in advance of said charge produced by said driving unit and said gate input capacitance accumulates therein said electric charges supplied by said at least one capacitor. 
     
     
       4. The semiconductor device according to  claim 2 , wherein said at least one capacitor is connected to said gate in advance of said charge produced by said driving unit and said gate input capacitance accumulates therein said electric charges supplied by said at least one capacitor. 
     
     
       5. The semiconductor device according to  claim 1 , wherein a gate voltage of said insulated gate transistor becomes not less than a threshold voltage with said electric charges supplied to said gate input capacitance by said at least one capacitor. 
     
     
       6. The semiconductor device according to  claim 1 , wherein a gate voltage of said insulated gate transistor becomes less than a threshold voltage by supplying said at least one capacitor with said electric charges accumulated in said gate input capacitance. 
     
     
       7. The semiconductor device according to  claim 5 , wherein a gate voltage of said insulated gate transistor becomes less than a threshold voltage by supplying said at least one capacitor with said electric charges accumulated in said gate input capacitance. 
     
     
       8. The semiconductor device according to  claim 1 , wherein the capacitance of said at least one capacitor is not less than twice as much as said gate input capacitance at the time when the Miller effect occurs. 
     
     
       9. The semiconductor device according to  claim 1 , wherein said at least one capacitor consists of a plurality of capacitors, and said plurality of capacitors are connected in parallel to one another when said electric charges accumulated in said gate input capacitance are supplied thereto and the plurality of capacitors are connected in series to one another when said electric charges accumulated therein are supplied to said gate input capacitance. 
     
     
       10. A method of driving a transistor, comprising the steps of: 
       (a) producing discharge of gate input capacitance in an insulated gate transistor; and  
       (b) producing charge of said gate input capacitance,  
       wherein said step (a) includes the steps of:  
       (c) supplying electric charges accumulated in said gate input capacitance to said capacitor and accumulating said electric charges supplied by said gate input capacitance in said capacitor; and  
       (d) extracting electric charges remaining in said gate input capacitance after said step (c), and  
       said step (b) includes the steps of:  
       (e) supplying electric charges accumulated in said capacitor to said gate input capacitance and accumulating said electric charges supplied by said capacitor in said gate input capacitance after said step (d); and  
       (f) further supplying electric charges to said gate input capacitance after said step (e).  
     
     
       11. The method of driving a transistor according to  claim 10 , further comprising the step of: 
       (g) charging said capacitor after said step (a) and before said step (b).  
     
     
       12. The method of driving a transistor according to  claim 10 , wherein 
       said gate input capacitance supplies said electric charges accumulated therein to said capacitor after a gate of said insulated gate transistor and said capacitor are connected to each other in said step (c),  
       said electric charges remaining in said gate input capacitance are extracted in said step (d) after said gate and said capacitor are disconnected from each other in said step (c),  
       said capacitor supplies said electric charges accumulated therein to said gate input capacitance after said gate and said capacitor are connected to each other in said step (e), and  
       said electric charges are further supplied to said gate input capacitance in said step (f) after said gate and said capacitor are disconnected from each other in said step (e).  
     
     
       13. The method of driving a transistor according to  claim 12 , wherein 
       a time period from connection of said gate to said capacitor in said step (c) to disconnection of said gate from said capacitor in said step (d) is not more than 5 .mu.s.  
     
     
       14. The method of driving a transistor according to  claim 12 , wherein 
       a time period from connection of said gate to said capacitor in said step (e) to disconnection of said gate from said capacitor in said step (f) is not more than 5 .mu.s.  
     
     
       15. The method of driving a transistor according to  claim 13 , wherein 
       a time period from connection of said gate to said capacitor in said step (e) to disconnection of said gate from said capacitor in said step (f) is not more than 5 .mu.s.